Bus Bar Assembly and Method of Manufacturing Same

ABSTRACT

A bus bar assembly includes a first main conductor, a second main conductor, and an insulator member provided between the main conductors. The insulator member includes: (i) an insulator component, (ii) a first conductor layer provided on the top surface of the insulator component, and (iii) a second conductor layer provided on the bottom surface of the insulator component, wherein the first conductor layer includes an outer edge around a perimeter thereof, wherein the outer edge is located at least a certain distance from the outer edge around the perimeter of the insulator component, wherein the second conductor layer includes an outer edge around a perimeter thereof, wherein the outer edge is located at least the same certain distance from the outer edge of the insulator component, and wherein the certain distance is sufficient to cause the bus bar assembly to satisfy the creepage requirement of the assembly.

GOVERNMENT CONTRACT

This invention was made with government support under U.S. Navy Contract(NAVSEA) N00024-07. The United States government may have certain rightsin the invention.

FIELD OF THE INVENTION

The present invention relates to bus bar devices, and in particular, toa bus bar assembly that includes a conductive cladding provided on theinsulator layer to increase the partial discharge inception voltage.

BACKGROUND OF THE INVENTION

A bus bar is a multilayer device that is commonly used for power and/orsignal distribution in electronic systems and power conversionequipment. Bus bars generally include at least two conductors (usuallyin the form of elongated strips or bars of a metal conductor such ascopper) separated by an insulating layer made of, for example, adielectric material. The conductors typically have a number ofdistribution pins extending therefrom which enable electricalconnections to be made between the conductors and the remainder of thecircuit components.

FIG. 1 is a cross-sectional view of a portion of a prior art bus barassembly 2. Bus bar assembly 2 includes a first main conductor 4 madeof, for example copper, a second main conductor 6 also made of, forexample copper, and an insulator layer 8 made of, for example, adielectric material, provided between the first main conductor 4 and thesecond main conductor 6. Typically, air 10 is trapped in small air voidsthat exist between first main conductor 4 and insulator layer 8 andbetween second main conductor 6 and insulator layer 8. Air 10 in the airvoids frequently leads to a plasma creation in the air voids known aspartial discharge. The Partial discharge is problematic as it slowlybreaks down the material of insulator layer 10. The partial dischargeeffect is caused by the high field strength that is used in a dielectricinsulator, and is exacerbated by the relative dielectric constant ofinsulator layer 8 as compared to the dielectric constant of air 10,which causes the field to concentrate in the small air voids. While thisdoes not lead to an arc, it does lead to the plasma creation known aspartial discharge.

There is thus a need for a bus bar assembly that decreases thelikelihood of the occurrence of partial discharge in the bus barassembly.

SUMMARY OF THE INVENTION

In one embodiment, a bus bar assembly for use in an application having acreepage distance requirement is provided that includes a first mainconductor, a second main conductor, and an insulator member providedbetween the first main conductor and the second main conductor. Theinsulator member includes: (i) an insulator component having a topsurface, a bottom surface, and a first outer edge around a perimeterthereof, (ii) a first conductor layer provided on the top surface of theinsulator component, and (iii) a second conductor layer provided on thebottom surface of the insulator component, wherein the first conductorlayer includes a second outer edge around a perimeter thereof, whereinthe second outer edge is located at least a certain distance from thefirst outer edge around the perimeter of the insulator component,wherein the second conductor layer includes a third outer edge around aperimeter thereof, wherein the third outer edge is located at least thecertain distance from the first outer edge around the perimeter of theinsulator component, and wherein the certain distance is sufficient tocause the bus bar assembly to satisfy the creepage requirement.

In another embodiment, a method of making a bus bar assembly is providedthat includes determining a creepage distance requirement for the busbar assembly, forming an insulator member as just described, andaffixing the insulator member between a first main conductor and secondmain conductor.

Therefore, it should now be apparent that the invention substantiallyachieves all the above aspects and advantages. Additional aspects andadvantages of the invention will be set forth in the description thatfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Moreover, the aspects andadvantages of the invention may be realized and obtained by means of theinstrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description given below, serve to explain the principles ofthe invention. As shown throughout the drawings, like reference numeralsdesignate like or corresponding parts.

FIG. 1 is a cross-sectional view of a portion of a prior art bus barassembly;

FIG. 2A is an exploded view and FIG. 2B is an isometric view of aportion of a bus bar assembly according to one exemplary embodiment ofthe present invention;

FIG. 3 is a cross-sectional view of the bus bar assembly of FIG. 2 takenalong lines 3-3 in FIG. 2; and

FIG. 4 is a cross-sectional view of a portion of a bus bar assemblyaccording to an alternative exemplary embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example and withoutlimitation, top, bottom, left, right, upper, lower, front, back, andderivatives thereof, relate to the orientation of the elements shown inthe drawings and are not limiting upon the claims unless expresslyrecited therein.

As employed, herein, the statement that two or more parts or componentsare “coupled” together shall mean that the parts are joined or operatetogether either directly or through one or more intermediate parts orcomponents.

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

FIG. 2A is an exploded view and FIG. 2B is an isometric view of aportion of a bus bar assembly 12 according to one exemplary embodimentof the present invention. FIG. 3 is a cross-sectional view of bus barassembly 12 taken along lines 3-3 in FIG. 2A. Bus bar assembly 12includes a first main conductor 14 having distribution prongs or fingers15 and a second main conductor 16 having distribution prongs or fingers17. In the exemplary embodiment, first main conductor 14 and second mainconductor 16 are made of copper, although other suitable conductivematerials, such as other metals, may also be used. A plated insulatormember 18 is provided in between first main conductor 14 and second mainconductor 16.

As seen in FIGS. 2A, 2B and 3, plated insulator member 18 includesinsulator element 20 having a conductor layer 22A provided on a topsurface thereof and a conductor layer 22B provided on a bottom surfacethereof In the exemplary embodiment, insulator element 20 is sheet ofdielectric material such as, without limitation, FR-4, GPO-2 or GPO-3,or ceramic dielectric material. Also in the exemplary, non-limitingembodiment, plated insulator member 18 is made by plating conductorlayer 22A on the top surface of insulator element 20 and platingconductor layer 22B on the bottom surface of insulator element 20 ismade by plating conductor layers 22A, 22B onto insulator element 20using any suitable metal plating technique, such as any of a number ofknown plating techniques used in printed circuit board manufacture tolay metallization onto a dielectric substrate such as FR-4. Thedeposition of conductor layers 22A, 22B onto insulator element 20 asjust described will shift the charge point to the surface of each ofconductor layers 22A, 22B. In the exemplary embodiment, the platingprocess will ensure that no air is trapped between conductor layer 22Aand the top surface of insulator element 20 or between conductor layer22B and the bottom surface of insulator element 20 (i.e., thepossibility of entrained air or voids is eliminated). Alternatively,conductor layers 22A, 22B may be deposited on the respective surfaces ofinsulator element 20 using other suitable deposition methods, such as,without limitation, vapor deposition or sputtering, wherein no air istrapped between conductor layer 22A and the top surface of insulatorelement 20 or between conductor layer 22B and the bottom surface ofinsulator element 20.

The metallization deposited on both the top and bottom surfaces ofinsulator element 20 is then etched back from each of the outer edges 24of insulator element 20 by an amount/distance that will make thecreepage distance for bus bar assembly 12, when finally assembled asdescribed herein, appropriate for the given application, thereby formingplated insulator member 18. In the exemplary, non-limiting embodimentshown in FIGS. 2A, 2B and 3, the plating on both the top and bottomsurfaces of insulator element 20 is etched back an amount/distance ateach outer edge location 24 that will result in conductor layer 22Abeing aligned with the adjacent outer edge portion 26 (not includingprongs 15) of first main conductor 14 and conductor layer 22B beingaligned with the adjacent outer edge portion 28 (not including prongs17) of second main conductor 16 when bus bar assembly 12 is assembled asdescribed below. In the exemplary, non-limiting embodiment, theremaining plating comprising conductor layers 22A, 22B are then tinnedor plated to prevent corrosion.

In an alternative embodiment, rather than the metallization being etchedback as just described, the metallization is selectively deposited onboth the top and bottom surfaces of insulator element 20 in a mannerwherein conductor layer 22A is aligned with the adjacent outer edgeportion 26 (not including prongs 15) of first main conductor 14 andconductor layer 22B is aligned with the adjacent outer edge portion 28(not including prongs 17) of second main conductor 16 when the bus barassembly 12 is assembled.

After plated insulator member 18 is formed as just described, first mainconductor 14 is coupled to the top surface of plated insulator member 18on top of conductor layer 22A in a manner wherein first main conductor14 is electrically coupled to conductor layer 22A and second mainconductor 16 is coupled to the bottom surface of plated insulator member18 on top of conductor layer 22B in a manner wherein second mainconductor 16 is electrically coupled to conductor layer 22B. In theexemplary embodiment, this is accomplished by sandwiching platedinsulator member 18 between first and second main conductors 14, 16using, for example, a non-conductive clamp or bracket, although othersuitable affixation methods (e.g., an adhesive) may also be employed. Ascan be seen in FIG. 3, due to the etching back of the metallization toform conductor layers 22A, 22B, bus bar assembly 12 will include anoverhanging insulator portion 30 that extends beyond both first andsecond main conductors 14, 16 and the conductor layers 22A, 22B aroundthe outer perimeter of bus bar assembly 12. As noted above, overhanginginsulator portion 30 will increase the surface path distance betweenfirst and second main conductors 14, 16 and, depending on the amount ofetching selectively performed, enable bus bar assembly 12 to satisfy thecreepage distance requirements of the application for which it is beingmade. In any particular application, the required creepage distance isdetermined by the voltage that will be applied to the two conductors(first and second main conductors 14, 16) and whatever standard isappropriate (e.g., IEC or UL). More fundamentally, the required creepagedistance is determined to prevent arcing between the two conductorsunder reasonable cases of contamination and air quality. Typically, thisis anywhere from 0.5 inches for low voltages (<1 kV), several inches formedium voltages (e.g., 1-30 kV), and several feet for high voltages (>30kV). In addition, the required creepage distance is typically greaterthan the required air gap between two conductors because an arc maytravel across moisture or other contaminates deposited on the surface.

Moreover, by including plated insulator member 18 as just described, theinception voltage of partial discharge for bus bar assembly 12 will beincreased significantly, thereby reducing the likelihood thatdetrimental partial discharge will occur. Furthermore, if air is trappedbetween first main conductor 14 and conductor layer 22A and/or betweensecond main conductor 16 and conductor layer 22B, partial dischargethere between will be prevented because both surfaces will be at thesame potential.

FIG. 4 is a cross-sectional view of a portion of a bus bar assembly 12′according to an alternative exemplary embodiment of the presentinvention. Bus bar assembly 12′ includes a number of the same componentsas bus bar assembly 12, and like components are labeled with likereference numerals in FIG. 4. As seen in FIG. 4, bus bar assembly 12′ afirst main conductor 14 and a second main conductor 16 which, in theexemplary embodiment, are made of copper, although other suitableconductive materials, such as other metals, may also be used. InAddition, a plurality of plated insulator members 18 as describedelsewhere herein are provided in between first main conductor 14 andsecond main conductor 16. In the illustrated embodiment, four platedinsulator members 18A, 18B, 18C and 18D are provided in between firstmain conductor 14 and second main conductor 16, although more or lessplated insulator members 18 may also be used within the scope of thepresent invention. As described elsewhere herein, the conductor layers22 on each plated insulator member 18 are formed by depositing aconductive material on the respective surface of the plated insulatormember 18 and etching that conductive material back from the edge of theassociated insulator element 20 so that overhanging insulator portion 32comprising a plurality of overhanging insulator portions 30 will beformed when bus bar assembly 12′ is assembled. In the exemplaryembodiment, bus bar assembly 12′ is assembled by sandwiching platedinsulator members 18A, 18B, 18C, 18D between first and second mainconductors 14, 16 using, for example, a non-conductive clamp or bracket,although other suitable affixation methods (e.g., an adhesive) may alsobe employed. Overhanging insulator portion 32 comprising the pluralityof overhanging insulator portions 30 will increase the surface pathdistance between first and second main conductors 14, 16 and, dependingon the amount of etching selectively performed, enable bus bar assembly12′ to satisfy the creepage distance requirements of the application forwhich it is being made.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,deletions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as limited by theforegoing description but is only limited by the scope of the appendedclaims.

1. A bus bar assembly for use in an application having a creepagedistance requirement, comprising: a first main conductor; a second mainconductor; and an insulator member provided between the first mainconductor and the second main conductor, the insulator member including(i) an insulator component having a top surface, a bottom surface, and afirst outer edge around a perimeter thereof, (ii) a first conductorlayer provided on the top surface of the insulator component, and (iii)a second conductor layer provided on the bottom surface of the insulatorcomponent, wherein the first conductor layer includes a second outeredge around a perimeter thereof, wherein the second outer edge islocated at least a certain distance from the first outer edge around theperimeter of the insulator component, wherein the second conductor layerincludes a third outer edge around a perimeter thereof, wherein thethird outer edge is located at least the certain distance from the firstouter edge around the perimeter of the insulator component, and whereinthe certain distance is sufficient to cause the bus bar assembly tosatisfy the creepage requirement.
 2. The bus bar assembly according toclaim 1, wherein no air is trapped between the first conductor layer andthe top surface of the insulator component, and wherein no air istrapped between the second conductor layer and the bottom surface of theinsulator component.
 3. The bus bar assembly according to claim 1,wherein the first conductor layer is formed by depositing a firstconductive material onto the top surface of the insulator component andremoving a portion of the first conductive material such that the secondouter edge of the first conductor layer is located at least the certaindistance from the first outer edge around the perimeter of the insulatorcomponent, and wherein the second conductor layer is formed bydepositing a second conductive material onto the bottom surface of theinsulator component and removing a portion of the second conductivematerial such that the third outer edge of the second conductor layer islocated at least the certain distance from the first outer edge aroundthe perimeter of the insulator component.
 4. The bus bar assemblyaccording to claim 3, wherein the depositing a first conductive materialonto the top surface comprises plating, vapor depositing or sputteringthe first conductive material onto the top surface, and wherein thedepositing a second conductive material onto the top surface comprisesplating, vapor depositing or sputtering the second conductive materialonto the top surface.
 5. The bus bar assembly according to claim 3,wherein the removing a portion of the first conductive materialcomprises etching away the portion of the first conductive material, andwherein the removing a portion of the second conductive materialcomprises etching away the portion of the second conductive material. 6.The bus bar assembly according to claim 1, wherein the first and secondconductive materials are copper.
 7. The bus bar assembly according toclaim 1, wherein the insulator component is a dielectric.
 8. The bus barassembly according to claim 7, wherein the insulator component is asheet of dielectric material selected from the group consisting of FR-4,GPO-2, GPO-3, and a ceramic dielectric material.
 9. The bus bar assemblyaccording to claim 1, wherein the first conductor includes a first outerconductor edge, wherein the second conductor includes a second outerconductor edge, and wherein the insulator component extends beyond andoverhangs the first outer conductor edge and the second outer conductoredge.
 10. The bus bar assembly according to claim 1, wherein the firstconductor includes a plurality of first outer conductor edges, whereinthe second conductor includes a plurality of second outer conductoredges, and wherein the insulator component extends beyond and overhangseach of the first outer conductor edges and each of the second outerconductor edges.
 11. The bus bar assembly according to claim 1, whereinthe insulator member further includes a plurality of additionalinsulator components each having a top surface, a bottom surface, and anadditional first outer edge around a perimeter thereof, wherein for eachadditional insulator component (i) a first additional conductor layer isprovided on the top surface of the additional insulator component, and(ii) a second additional conductor layer is provided on the bottomsurface of the additional insulator component, wherein each firstadditional conductor layer includes an additional second outer edgearound a perimeter thereof, wherein the additional second outer edge islocated at least the certain distance from the additional first outeredge around the perimeter of the additional insulator component, whereineach second additional conductor layer includes an additional thirdouter edge around a perimeter thereof, wherein the additional thirdouter edge is located at least the certain distance from the additionalfirst outer edge around the perimeter of the additional insulatorcomponent, and wherein the certain distance is sufficient to cause thebus bar assembly to satisfy the creepage requirement.
 12. The bus barassembly according to claim 11, wherein the plurality of additionalinsulator components comprises three additional insulator components.13. The bus bar assembly according to claim 1, wherein the firstconductor layer is formed by depositing a first conductive material ontothe top surface of the insulator component in a manner such that thesecond outer edge of the first conductor layer is located at least thecertain distance from the first outer edge around the perimeter of theinsulator component, and wherein the second conductor layer is formed bydepositing a second conductive material onto the bottom surface of theinsulator component in a manner such that the third outer edge of thesecond conductor layer is located at least the certain distance from thefirst outer edge around the perimeter of the insulator component.
 14. Amethod of making a bus bar assembly, comprising: determining a creepagedistance requirement for the bus bar assembly; forming an insulatormember by providing a first conductor layer on a top surface of aninsulator component and a second conductor layer on a bottom surface ofthe insulator component, wherein the insulator component has a firstouter edge around a perimeter thereof, wherein the first conductor layerincludes a second outer edge around a perimeter thereof, wherein thesecond outer edge is located at least a certain distance from the firstouter edge around the perimeter of the insulator component, wherein thesecond conductor layer includes a third outer edge around a perimeterthereof, wherein the third outer edge is located at least the certaindistance from the first outer edge around the perimeter of the insulatorcomponent, and wherein the certain distance is sufficient to cause thebus bar assembly to satisfy the creepage requirement; and affixing theinsulator member between a first main conductor and second mainconductor.
 15. The method according to claim 14, wherein following theproviding step no air is trapped between the first conductor layer andthe top surface of the insulator component and no air is trapped betweenthe second conductor layer and the bottom surface of the insulatorcomponent.
 16. The method according to claim 14, wherein the providingstep comprises depositing a first conductive material onto the topsurface of the insulator component and removing a portion of the firstconductive material such that the second outer edge of the firstconductor layer is located at least the certain distance from the firstouter edge around the perimeter of the insulator component anddepositing a second conductive material onto the bottom surface of theinsulator component and removing a portion of the second conductivematerial such that the third outer edge of the second conductor layer islocated at least the certain distance from the first outer edge aroundthe perimeter of the insulator component.
 17. The method according toclaim 16, wherein the depositing a first conductive material onto thetop surface comprises plating, vapor depositing or sputtering the firstconductive material onto the top surface, and wherein the depositing asecond conductive material onto the top surface comprises plating, vapordepositing or sputtering the second conductive material onto the topsurface.
 18. The method according to claim 16, wherein the removing aportion of the first conductive material comprises etching away theportion of the first conductive material, and wherein the removing aportion of the second conductive material comprises etching away theportion of the second conductive material.
 19. The method according toclaim 14, wherein the first conductor includes a first outer conductoredge, wherein the second conductor includes a second outer conductoredge, and wherein the insulator component extends beyond and overhangsthe first outer conductor edge and the second outer conductor edge. 20.The method according to claim 14, wherein the first conductor includes aplurality of first outer conductor edges, wherein the second conductorincludes a plurality of second outer conductor edges, and wherein theinsulator component extends beyond and overhangs each of the first outerconductor edges and each of the second outer conductor edges.
 21. Themethod according to claim 14, wherein the providing step comprisesdepositing a first conductive material onto the top surface of theinsulator component in a manner such that the second outer edge of thefirst conductor layer is located at least the certain distance from thefirst outer edge around the perimeter of the insulator component anddepositing a second conductive material onto the bottom surface of theinsulator component in a manner such that the third outer edge of thesecond conductor layer is located at least the certain distance from thefirst outer edge around the perimeter of the insulator component.